The present invention relates to a system for indicating as time the taken-up length or remaining length of a tape recording medium in an apparatus using such a tape recording medium, and more particularly to a system for indicating as time the taken-up length or remaining length of the tape suitable for a magnetic recording-reproduction apparatus such as an audio tape recorder or a video tape recorder using a tape contained in a cartridge or a cassette.
In conventional magnetic recording-reproduction apparatuses such as a video tape recorder or an audio tape recorder, the length taken-up of the tape recording medium, i.e., the length thereof wound through the recorder, is indicated generally by use of a device called a tape counter. In this tape counter, the rotation of the reels is transmitted to a mechanical revolutions counter through a belt or the like, thus indicating the number of reel revolutions in three or four digits. Such a tape counter has problems as mentioned below.
(1) The taken-up tape length is indicated indirectly by the number of reel revolutions, and the rotational speed of the reels depends on the amount of tape which is unwound, thus making it impossible to indicate the taken-up tape length in terms of time.
(2) In the case where a reel partly wound with tape is loaded, it is impossible to detect the remaining tape length.
(3) It is impossible to search the tape for a point associated with a given point in time.
The conventional tape counter has the above-mentioned shortcomings and therefore the exact time length or point cannot be determined by the tape counter. The user must determine the amount of tape taken up visually by experience. As a result, it often happens that the remaining tape length is not sufficient to record the whole of the desired program or it is almost impossible to search for a desired point midway of the recorded part of the tape by one fast forward or one rewind mode of operation but the fast forward or the rewind mode of operation or reproduction must be repeated several times in order to find the desired point of the tape, resulting in the disadvantage of handling inconvenience.